The present disclosure generally relates to metal contact etch patterning in semiconductor integrated circuits. More particularly, the present disclosure relates to metal contact etch patterning with a transition step using closed-loop feedback.
In metal contact (CA) etch patterning, the process window is quite narrow in sub-45 nm devices, for example. A typical goal is to achieve a final critical dimension (FCD) that is as small as possible without incurring an open-failure, such that an overlay margin can be extended. Earlier approaches to the etch process generally had to shrink the critical dimension (CD) over a 20 nm bias. Thus, polymerizing gas chemistry has been applied to the etch process. Prior approaches attempted to pre-select a gas flow rate to achieve such a CD. Unfortunately, the smaller the CD using this approach, the higher the risk of open-failures.